Migrate to Shoehorn

as

@total-typescript/shoehorn

When to use this skill

• Modernizing test code to eliminate

  as

  type assertion anti-patterns
• Making test data creation type-safe with autocomplete support
• Migrating from

  as unknown as Type

  double-assertions

When not to use this skill

• Production code (shoehorn is test code only)
• Non-TypeScript projects
• Runtime type validation → use a library like

  zod

Installation

npm i @total-typescript/shoehorn

The three functions

fromPartial<T>(partial)

— incomplete objects

// Before (unsafe)
const user = { name: "Alice" } as User

// After (type-safe, keeps autocomplete)
import { fromPartial } from "@total-typescript/shoehorn"
const user = fromPartial<User>({ name: "Alice" })

fromAny<T>(value)

— intentionally wrong data

// Before (verbose double-as)
const badInput = { invalid: true } as unknown as User

// After
import { fromAny } from "@total-typescript/shoehorn"
const badInput = fromAny<User>({ invalid: true })

fromExact<T>(complete)

— enforced complete objects

// Before
const user = { name: "Alice", email: "alice@example.com", id: 1 } as User

// After (TypeScript will error if any field is missing)
import { fromExact } from "@total-typescript/shoehorn"
const user = fromExact<User>({ name: "Alice", email: "alice@example.com", id: 1 })

Migration workflow

1. Find all

as

assertions in test files

grep -rn " as " --include="*.test.ts" --include="*.spec.ts" --include="*.test.tsx"

2. Classify each assertion

• Partial object, only some fields needed →

  fromPartial()

• Intentionally wrong/invalid data →

  fromAny()

• Complete object, all fields present →

  fromExact()

3. Replace and add import

import { fromPartial, fromAny, fromExact } from "@total-typescript/shoehorn"

4. Verify TypeScript still compiles

npx tsc --noEmit

Critical constraint

fromPartial

fromAny

fromExact

Instructions

1. Identify the task trigger and expected output.
2. Follow the workflow steps in this skill from top to bottom.
3. Validate outputs before moving to the next step.
4. Capture blockers and fallback path if any step fails.

Examples

• Example: Apply this skill to a small scope first, then scale to full scope after validation passes.

Best practices

• Keep outputs deterministic and auditable.
• Prefer small reversible changes over broad risky edits.
• Record assumptions explicitly.

References

• Project standards:

  .agent-skills/skill-standardization/SKILL.md

• Validator script:

  .agent-skills/skill-standardization/scripts/validate_skill.sh